If you're in a bad mood you may really want to take a few deep breaths and go for a walk.
Iowa State University scientists had a group of students either go on a walking tour of campus, or sit and look at photographs of the campus. Ultimately, those who walked reported being in a better mood following the experiment compared to the non-walking group.
The effect even stuck in a second experiment when researchers induced a feeling of dread in the participants before their walk by telling them they had to write a two-page essay afterwards. They say walking makes us feel good because our ancestors associated physical movement with hunting and gathering, which meant finding food.